1. Field of the Invention
The present invention relates to an information recording medium, such as an optical disk, on which digital data is recorded with high density. Moreover, the present invention relates to an information recording apparatus which records digital data on such an information recording medium with high density. Furthermore, the present invention relates to an information reproducing apparatus which reproduces digital data recorded with high density on such an information recording medium.
2. Description of the Related Art
As is well known, in recent years, television (TV) broadcasting has shifted to the use of digital transmission, and there has accordingly been a demand for streamer equipment to record digital TV broadcasts.
Presently, as the data transfer form at of digital TV broadcast in Japan, the U.S., and Europe, the MPEG-transport stream (TS) defined mainly according to the moving picture image coding experts group (MPEG) standard is being used.
It is believed that an MPEG-TS system will be standardized in the field of digital broadcasting using moving images in future. Currently, as an apparatus which records digital broadcast data sent using MPEG-TS, the digital (D)-video home system (VHS), in which a tape is used as the recording medium, is being marketed. However, for convenience, there has been a demand for an apparatus in which an optical disk is used as the recording medium.
In general, digital TV broadcasts are received/reproduced by a set-top box (STB). The STB is an apparatus which subjects encrypted data to extension/reproduction processing based on a key distributed by a broadcast station.
When the received data is reproduced as such, a digital extension portion decrypts the data, an MPEG decoder portion decodes the data, and a video encoder portion converts the data to a TV signal and displays the data as a picture on a TV screen.
On the other hand, a method of storing the data comprises: transferring the digital data received from a tuner system as a bit stream to a recording apparatus via a digital interface such as the Institute of Electrical and Electronics Engineers (IEEE) 1394 Interface (I/F) without changing the state of the data; and recording the data on a recording medium.
Conversely, to reproduce the data recorded on the recording medium from the beginning or from midway, all the data is sent as such, and reproduced on the STB side. As content to be recorded, a plurality of programs are multiplexed and recorded in some cases. In the case, the desired program is selected and reproduced on the STB side.
As a recording apparatus now on sale, there is D-VHS in which tape media are used as the recording media. The tape media have a disadvantage that there is not random accessibility, and a problem is that a scene actually desired to be seen cannot momentarily be reproduced. Therefore, there has been an increasing demand for realization of the recording apparatus which uses high-capacity optical disk media such as Digital Versatile Disc (DVD)-Random Access Memory (RAM).
From the DVD forum, as of February, 2001, as a standard in which video information can be recorded or reproduced with respect to the information recording medium, “DVD Specifications for DVD-RAM/DVD-RW/DVD-R for General Discs Part 5: STREAM RECORDING” has been prepared.
Additionally, in this standard, to match concept with that of another DVD standard, a pseudo MPEG-Program Stream (PS) packet is constituted by one unit of 2 kilobytes (KB). Therefore, header information and access time information are added in a 2 KB unit, and as a result recording efficiency is lowered.
On the other hand, in the standard, access information is prepared as concentration information in order to effectively utilize the random accessibility of the optical disk. Additionally, the access information is basically prepared with respect to a certain given data amount to be recorded, or a data amount to be recorded by a given reproduction time unit. Therefore, when a recording capacity of the optical disk increases, an information amount also increases. This results in an increase of the capacity of a memory for storing information which has to be constantly held by the recording apparatus.